Chapter 2

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Chapter 2

Section 1:

Learning Objectives:

  • Describe Galileo's law of inertia
  • Apply Newton's first law of motion
  • Recognize inertial mass as a physical property of matter
  • Use examples to demonstrate that speed is always relative to some other object
  • Explain that the speed of an object depends on the reference frame from which it is being observed

What Do You See:

  • The boy is building up momentum to run and go kick the ball
  • The ball goes flying up over the goal
  • The boy just standing there kicks the ball and it only travels at a small distance
  • The mouse is trying to push the ball but it is not moving, and the bug is doing the same

What Do You Think?:

  • Figure skaters keep moving across the ice at high speeds for long times because there is not a lot of friction on the ice. Ice has very little friction.
  • Because of newtons law, an object in motion will stay in motion. There is a force acting on that starts it moving and it doesn't stop right away because this object in motion wants to stay in motion

Summary Homework:

The NASA scientists announced that their Kepler telescopes found plant located in the habitable zone around its star. Its called Kepler-22b, and has a surface temperature of 70 degrees and has the capability of having water. The finding of this planet brought up many questions like what is the composition of the planet’s surface? Is it rocky, primarily liquid, or gaseous. They don’t yet know the answer to that question. The planet’s mass has not yet been estimated. The scientists will have a better idea this summer of 2012. When the Kepler field is visible again during the night time, they will need to get the mass of Kepler-22b and combine it with the the measured diameter of Kepler-22b to get a density from which we can guess at the planet’s composition

Investigate 2.1

1a.)Starting point: 30 cm.
1b.) When released it reached a height of 29.5cm
2a.) The ball will go about half way up the right side if released halfway up the left side. Starting at 20cm the ball will go up 20cm on the other side.
3a.) My prediction was right becasue it reached the height at which it was released at. My prediction was veyr close but there is still uncertainty because of the random error.
3b.) With the measurements it did actually go to the same spot. When it was dropped from a height of 20 cm, the ball reached a same height of 20 cm on the other side.
5a.) No because it is losing some energy because its losing friction. It is going to a flat area and will never have as much energy that it began with.
5b.) The ball will roll until something else stops like the wall or friction.
5c.) The lack of friction and lack of forces will keep the ball rolling.

Do Now 12/9/11:

  • With no friction he will reach same 4 meters on the other side becasue the energy will not ever be more than what it began with.
  • With friction he will reach close but not all the way to the 4 meters.
  • This scenario illustrates Newton 1st law of motion because if there is no force acting on it, it will go all the way up, but if there is a force acting on it, it will get close but not all the way.

Physics Talk:

Newton's First Law of Motion:
Galileo's Law Of Inertia:
  • Galileo did a "thought experiment" where he imagined a ball made of extremely hard material set into motion on a horizontal, smooth surface. just life our investigate
  • He concluded that the ball would continue its motion on the horizontal surface with constant speed along a straight line to forever
  • Galileo formed the law of inertia
  • Inertia is the natural tendency of an object to remain at rest or to remain moving with constant speed in a straight line.
  • moving objects might continue to move forever unless a force, a push or a pull, stopped them.
Newton’s First Law of Motion:
  • Newton used Galileo’s law of inertia as the basis for making his first law of motion
  • An object at rest remains at rest, and an object already in motion remains in
    motion with constant speed in a straight-line path.
  • Newton also explained that an object’s mass is a measure of its inertia, or tendency to resist a change in motion
  • Given different masses moving at the same speed, the one with the greatest mass has the greatest inertia
  • Example: An empty grocery cart has a mass of 10 kg and a cart full of groceries has a mass of 30 kg. The cart with the greater mass has greater inertia.
Running Starts:
  • In sports, where the objective is to maximize the speed of an object or the distance traveled in air, the prior motion of a running start is very important.
  • Example:
  • In the javelin throw, an athlete is running holding a javelin. At the instance of release, the speed of the javelin is the same as the speed of the hand that is throwing the javelin.
  • Speed: the change in distance per unit of time.
  • Velocity: speed in a given direction.
  • Acceleration: the change in velocity per unit of time.
  • When a force acts, the speeds change.
Frames Of Reference:
  • If you run with a ball prior to throwing it, the ball gets your speed before you even try to release it.
  • Frame Of Reference: a vantage point with respect to which position and motion may be described.
  • When the speed is relative to the ground, this is not specifically stated and you are expected to assume this fact
  • If your frame of reference is the ground, then it all seems quite obvious. Frame of reference is a vantage point with respect to which position and motion may be described.
  • In sports, where you want to provide the greatest speed to a baseball, lacrosse ball, football, or a tennis ball, that speed could be increased if you were able to get on a moving platform.
  • An athlete will try to get the body moving with a running start, if allowed. If the running start is not permitted, the athlete tries to move every part of his or her body to get the greatest speed.

Checking Up:

1.) Inertia is the natural tendency of an object to remain at rest or to remain moving with constant speed in a straight line.
2.) Newtons first law of motion is when an object is at rest it will stay at rest and when an object is in motion it will stay in motion.
3.) A force needs to act on an object to stop it from moving at a constant speed.
4.) Gravity and friction stop the movement of the ball.
5.) The one with the larger mass will have the greater inertia.
6.) It is important to establish a frame of reference when describing the speed of the ball because

Section 2:

Learning Objectives:

  • Give example of distance, time, speed, and acceleration.
  • Differentiate between instantaneous speed and average speed.
  • Recognize when motion is accelerated.
  • Calculate average speed and acceleration.

What Do You See?:

  • When the boy is walking at a normal constant speed, the footprints are closer together.
  • When the boy is running at a constant speed, the footprints are further apart.
  • Footprints are like the strobe photos.

What Do You Think?:

  • it will cover over 100 miles per hour which is equal to 45 meters per second.

Investigate 2.2:

1a.) There will be an equal distance between the dots.
1b.) There will be an equal distance between the dots but they will be more spread out.
1c.) There will be an equal distance between the dots but they will be more closer together.
1d.) I think that the dots will go from having an equal distance to the distances between the dots growing closer together.

Section 3:

Learning Outcomes:

  • Identify the forces acting on an object
  • Determine when the forces on an object are either balanced or unbalanced
  • Compare amounts of acceleration semi-quantitatively
  • Apply Newton's second law of motion
  • Apply the definition of the newton as a unit of force
  • Describe weights as the force due to gravity on an object

What Do You See?:

  • The person is moving the ball with the stick.
  • She has to move faster to keep in contact with the ball
  • acceleration

What Do You Think?:

  • Force is a push or pull on an object
  • The tennis ball and the bowling ball have different masses. The ball with the bigger mass will be less affected by the force.

Investigate 2.3:

2a.) The motion of the cart is straight at a constant speed.
3a.) It goes faster.
3b.) They both moved the cart and the speed increased.
3c.)The small bend doesn't push the cart as far
3d.) the greater constant force pushing on an object, the cart the further the cart goes and speeds up.
4a.) A pencil with a very small mass, moved a lot further and quicker than the cart.
5a.) The heavier the object, it doesn't go as far, we used a graphing calculator and it did not move.
5b.) When equal amounts of a constant force are used to push objects having different masses, the more massive object will move less.
6a.) That large objects wont go anywhere, and small will move further.
8a.) The ruler will bend a little.
9a.) You couldn't add any more than five coins without them all falling off the ruler
9b.) One penny represents a small force, and large force represents five
9c.) The mass of the coins is causing the ruler to bend

Physics Talk:

Equation Of Newton's Second Law Of Motion:
  • Acceleration = FORCE divided by MASS
  • Acceleration is expresses in m/s2, force is expressed in Newtons, and mass is expressed in kilograms
Where There's Acceleration, There Must Be An Unbalanced Force:
  • Newton's second law tells you that accelerations are causes by unbalanced forces.
  • It doesn't matter what kind of force it is or how it originates
  • If you apply a force to an object that has a small mass, the acceleration may be quite large
  • If the object has a large mass, the acceleration will be smaller for the same force
  • Sometimes too small to measure
Gravity, Mass, Weight, and Newton's Second Law:
  • The Force of gravity
  • You cannot see the force, but you know its there based on observations that you make
  • Force of gravity acting on mass
  • Example: if you put a backpack on your back you can feel the force
  • Weight is the force of gravity acting on an object, and it depends on the mass of an object and the acceleration due to gravity
  • Weight: the vertical downward force exerted on a mass as a result of gravity
  • weight= mass x gravity(9.8m/s2)
Balanced and Unbalanced Forces:
  • When two forces act at the same time, the directions well as the magnitude of the forces determine the motion of the object
  • If the forces are in the same direction, then the sum of the forces or net force will cause a larger acceleration than either force alone

Checking Up:

1.) Newtons Second Law of Motion is force is equal to mass times the weight.
2.) By increasing an objects mass the acceleration of the object will the slower.
3.) If an object weighs 30N, I know that the mass of the object is negative since gravity is negative 9.8. negative times a negative is a positive.
4.)Your weight would be higher.

Physics To Go:

In notebook

Section 4:

Learning Outcomes:

  • Apply the terms free fall, projectile, trajectory, and range
  • Provide evidence concerning projectiles launched horizontally from the same height at different launch speeds (including zero launch speed_)
  • Explain the relation shop between the vertical and horizontal components of a projectile's motion
  • Recognize the factors that affect the range of a projectile
  • Infer the shape of a projectile's trajectory

What Do You See?:

  • The girl is dropping apples from the top of the ladder.
  • One apple is being dropped straight down and the other apple is being tossed
  • The boy is timing both apples to see that they will land at the same time

What Do You Think?:

Investigate: (part a for hw)

1a.) yes they do
2a.) yes they do
3a.) no because if theyre both horizontal it will hit at the same time
3b.) yes because it will go further
3c.) in notebook
4a.) at the same time
4b.) makes it go further

Section 6:

Learning Objections:

  • Provide evidence that forces come in pairs, with each force acting on a different object
  • Use newton's third law to analyze physical situations
  • Describe how Newton's third law explains much of the motion in your everyday life

What Do You See?:

  • the boy has his legs bent and up against the wall while sitting on a wheely chair
  • He pushed off the wall with his feet and rolls back

What Do You Think?:

  • When you jump up you should apply the force onto the ground and the ground will push back on you to make you jump

Investigate:

Part A:
1a. It is accelerated when it is being pushed by an outside force.You accelerate in the opposite direction.
1b. You are at a constant speed when there is no object or force acting on it.
1c. The wall was the source of the force.
1d. The chair was pushed straight in front of me.
1e. They are the same.
2a. He is moving straight back by pushing his feet off the wall.
2b. The wall
2c.He is being pushed by another student making him go backwards in the opposite direction of the other student.
2d. The force of Cory's hand pushing him made him be able to accelerate.
3a. the forward force comes from the ground.
3b. It wouldn't be possible to walk on ice with reg shoes because it would be very slippery and there would be no friction or force provided. With the skates it provides a friction with the ice that keeps you from slipping, and a force that pushes you off to skate.
4a. The force needs to be equal. When they were trying to pull the weight so that it would be equal the person with the larger amount of force made the other person not be able to pull as much to their opposite side, but come towards them.
Part B:
3a.) When the washer is placed on the meter sticky, the stick shakes at the slightest amount.
4a.) 0g- 11.7cm
100g- Shakes lightly- 11.5cm
350g- It starts to bend a little- 11.3cm
850g- The meter stick is bent- 11cm
4b.) The more weight applied to the meter stick, the more that the meter stick will bend (picture in notebook)
4c.) As the washer is placed, the meter stick is bending at the slightest amount, not as noticeable as the weights
4d.) Picture in notebook

Physics Talk:

  • Normal force is the force acting on an object is perpendicular to the surface the object is in contact with.
  • Frictional force is the force acting on an object from a surface that resists the motion of an object
  • Acceleration is always accompanied by an unbalanced force, and the acceleration and the force are in the same direction
  • Newton's Third Law
    • Forces come in pairs, the force of object A on object B is equal in strength and opposite in direction to the force of object B on object A.
    • For every applied force, there is an equal and opposite force.
    • Forces always come in equal and opposite pairs.
    • Example is if you push on a wall the wall pushes on you with the same force.
    • An inanimate object can apply a force.
  • Center of mass is the point at which all the mass of an object is considered to be concentrated.
  • Free Body Diagram
    • A diagram showing the forces that are acting on an object.
    • It is used to show the relative strength and the direction of all forces acting on an object in a given situation.

Checking Up Questions:

  1. Newton's third law is forces that are equal and opposite
  2. The gravity and the ground
  3. A free body diagram illustrates the direction and amount of forces that are acting on an object

Physics To Go:

  1. Yes because the ball of a different weight is pushing against the hand

Section 7

Learning Objectives:

  • Apply the definition of the coefficient of sliding friction
  • Measure the coefficient of sliding friction between the soles of athletic shoes and a variety of surfaces
  • calculate the effects of frictional forces on the motion of objects

What Do You See:

  • The guy is pulling the shoe across the ice easily while using the force meter
  • On the beach the guy is pulling the shoe across the sand with a tougher time

What Do You Think

  • Some sports require shoes with friction and other sports require shoes with less friction.
  • Depending on the surface that you play on you need shoes for traction.

Investigate:

1a.) We used an UGG boot. The weight of the boot is 4.5 Newtons.
1b.) The gravity, friction, and weight.
3a.) On top the of lab table. The surface is smooth and flat.
3b.) 1 N when dragged across the table.
3c.) 1N divided by 4.5 = .22N
4a.) 6N with shoe with weight
4b.) 6N divided by 4.5 = 1.3N
4c.)Yes because the heavier the
4d.) The heavier the athlete
5a.) 4N on the sandpaper
5b.)

Section 8

Learning Outcomes:

  • Apply equations for kinetic energy, gravitational, potential energy and elastic potential energy
  • Recognize that restoring forces are active when objects are deformed
  • Apply the equation for the force necessary to compress or stretch a spring
  • Measure the transformations among the different forms of energy
  • Conduct simulations of the transformations of energy involved in the pole vault

What Do You See?:

  • the person is running full speed with the pole vaulting stick in his hand
  • As he builds up speed and put the bottom of the stick to the ground the stick bends and when he lets go he gets thrown up to the top of the building

What Do You Think?:



Section 9

Learning Outcomes:

  • Measure changes in height of the body's center of mass during a vertical jump
  • calculate changes in the gravitational potential energy of the body's center of mass during a vertical jump
  • apply the definition of work
  • recognize how work is related to energy
  • apply the joule as a unit of work and energy using equivalent forms of the joule
  • describe the concepts of work and conservation of energy to the analysis of a vertical jump including weight, force, height, and time of flight

What Do You See?:

  • The ice skater is spinning around and jumped up
  • As he jumped up, he is still spinning
  • The person in the helicopter is timing the time that the skater is in the air.

What Do You Think?:

  • No

Investigate Section 9:

1a.) 21 frames of the skater in the air
1b.) 21/30 = .7
1c.) No it does not defy gravity
2a.) 32 frames of the basketball player in the air
2b.) 32/30=
3.) 130(4.3) = 569N